1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same, and more particularly, to a semiconductor device having a semiconductor layer used for adjusting the depth of a well, and the method of fabricating the same.
2. Description of the Prior Art
Electrically erasable programmable read only memory (EEPROM) is a kind of non-volatile memory. EEPROM can retain data even when the electricity supply is removed as well as having a re-record function. With the trend towards scaling down the size and increasing the integration of semiconductor devices, electronic products usually include a various internal semiconductor devices for meeting the requirements of low power consumption, fast response and low cost. Furthermore, each semiconductor device has its own performance and particular manufacturing process demands.
EEPROM may include metal-oxide-semiconductor transistors (MOS) and Schottky diodes. A Schottky diode is constructed by a metal-to-semiconductor interface where this interface is known to have rectifying characteristics. Moreover, a Schottky diode provides rectification as a result of unipolar current transport across the metal-semiconductor contact. For example, a Schottky diode's voltage drop at a forward bias of about 1 mA is in the rage of 0.15 V to 0.45 V, while the conventional silicon diode is about 0.6 V. Accordingly, the Schottky diode has the advantages of low threshold voltage and fast response speed when switching between forward and reverse bias voltage in comparison with the PN junction diode, and is therefore widely used for reducing power consumption and improving switching speed.
As the size of MOS is gradually minimized, how to improve the carrier mobility so as to elevate the response speed of the MOS has become a major topic for study in the semiconductor field.
How to integrate processes of different semiconductor devices such as MOS and Schottky diode to facilitate the functions of electronic products and save on manufacturing costs is another important issue in the field.